Hydraulic support systems for mine workings



April 1.4, 1970 G. BELL v 3,505,823

HYDRAULIC SUPPORT SYSTEMS Fon MINE WORKINGS l Filed July 18, 196B l` "A L1 I F|G.1 4', l 15'12 fr @l 2O g. 2O 5 76 n! 4 2o if iii i i *J 2() 5 13 2 L38 INVENTOR United States Patent Olhce 3,505,823 Patented Apr. 14, 1970 3,505,823 HYDRAULIC SUPPORT SYSTEMS FOR MINE WORKINGS Gnter Bell, 14 Heinrichstrasse, 4351 Horenburg, Germany Filed July 18, 1968, Ser. No. 745,865 Claims priority, application Germany, July 19, 1967,

Int. 'Cl. E21d 23/18 U.S. Cl. 61-45 2 4Claims ABSTRACT F THE DISCLOSURE Hydraulic roof support system for long wall faces of mines in which three frames form a self-advancing assembly and ram cylinders interconnect these frames for advancing either the center frame or the two outer frames. Two pairs of steering cylinders interlink the frames, which on pressurization act in opposite directions for correcting the positions of the frames, the chamber of annular cross section in one of each pair of steering cylinders being equal to the full cross section of the piston in the other steering cylinder of that pair. The chamber which comprises the full cross section of the piston in one steering cylinder is connected to the chamber of annular cross section in the associated cylinder.

The invention relates to a hydraulic roof support system for longwall faces in which the self-advancing frames are guided by steering cylinders to keep the frames parallel and to correct their alignment.

In such a roof support system appropriate operation of the steering cylinders ensures that the roof support system will continue to advance in a desired direction. The cylinders may also serve for realigning the frames of an assembly. In such arrangements it is essential that as many as possible of the controlling functions of the cylinders are automated to minimise the number of controls the operator is required to supervise at the face and to increase the productivity of the men that are still needed.

It has already been proposed to provide correcting cylinders operating at right angles to the roof bars for the purpose of keeping the frames of the roof support assembly in alignment. For aligning the frames of a twinframe walking assembly and for keeping them parallel it has also been proposed to attach such cylinders to the solebars for applying sideways thrust to a guiding slide. The guiding slide -may be anchored to the face conveyor yby an elastically llexible member or by a rope attached to a ram cylinder. Apart from the fact that the provision of a special guiding slide involves a relatively high eX- penditure in additional technical means it also complicates the control of such a system because the steering cylinders must be controlled both during advance of the frames and for realigning the frames.

On the other hand, in a roof support system for a longwall face, self-advancing assemblies comprising three parallel frames are also known in the art, in which a ram cylinder is interposed between each two frames. However, in such an arrangement alignment is not eifected vby steering cylinders but by spring elements between the frames. Another substantially similar proposal consists in providing telescopic steering rods containing springs for keeping neighbouring frames parallel. Both of these proposals necessitate the use of relatively large and powerful springs. These are expensive. A drawback in operation is the frequent generation of uncontrollable restoring forces released by the energy stored in the springs.

A hitherto unpublished earlier proposal combines each two telescopic steering rods in a pair to form a guiding assembly by connecting them by springs and ropes in such a way that normaly the fra-mes will be guided to maintain parallelism, but that realignment of the frames according to the position of the conveyor is still possible evenwhen the springs are deilected.

Summary of the invention A support system in which the members of three frames are disposed side by side. Either the two outer frames or the center frame advances. The center frame is connected to an abutment, which may be a conveyor. It is important that the conveyor travel along the coal seam under the influence of forces, which would be gravity in an inclined coal seam. The frames are required thus to follow the movement of the conveyor.

If the center frame advances, that frame must be in parallel relationship to the two outer frames and this is achieved by the steering cylinders since the respective rchambers of eao'h pair of steering cylinders is hydraulically connected and are o-f equal force.

If the conveyor moves downwardly along the seam, the center frame follows and it is then necessary to have an additional control for the steering cylinders.

In a roof support system according to the invention, control is therefore simplified because during normal advance, i.e. when the ram cylinders are operated, the steering cylinders work automatically. Not until the advancing action has been completed need the required correction be made by appropriately controlling the steering cylinders.

It is of course essential that the number of steering cylinders in the assembly should rbe as small as possible. In conventional forms of construction of such frames comprising a solebar, a roofbar and two props, the provision of two pairs of steering cylinders will be sufficient. The arrangement will preferably be such that the cylinders are attached to the upper ends of the prop cylinders. The attachment of the steering cylinders to the prop cylinders is advisable because the provision of links, anchoring straps, and the like to the ram of the prop will generally be impossible.

Brief description of the drawings FIGURE 1 is an assembly according to the invention in side elevation,

FIGURE 2 is a plan of the assembly according to FIG- URE l, and

FIGURE 3 is a plan, as in FIGURE 2, of an assembly according to the invention with a schematic representation of the associated hydraulic circuit, for controlling the steering cylinders.

Description of the preferred embodiment With reference to FIGURES l and 2 it will be understood that the roof supports shown in these drawings constitute only part of a hydraulic roof support system which consists of a plurality of self-advancing assemblies placed side-by-side of which the figures shown only the frames A, B, C of one assembly. In the illustrated embodiment each frame comprises a roofbar 1, which has a downwardly projecting cantilever end for forepoling across a face conveyor 2a and two props 2 on a solebar 3.

The three frames A, B and C are associated side-byside to form a self-advancing assembly. In the illustrated embodiment, the waste-side props of the two frames A and C and the coal-face-side props of the frames A and C are interconnected by spring steel cross bars 4 and 5, whereas the frames A and B as well as B and C are connected by ram cylinders 6 and 7.

These two ram cylinders `6 and 7 of which the ram of one cylinder is pivotably attached to frame lB and the cylinder end to frame A, whereas the ram of the other cylinder 7 is pivotably attached to frame B and its cylinder end to frame C, operate to advance the roof support, assembly in walking steps.

'The assembly is tied to the face conveyor 2a by a rope 8. One end of the rope 8 is anchored to the conveyor, whereas its other end is attached to the ram of a third ram cylinder 9 which is itself attached to the frame B in the centre.

For advancing the assembly, the ram cylinder 9 is pressurised and thus causes the centre frame B to be moved forwards towards the face conveyor 2a into the position shown in FIGURE 3, whilst the two other frames A and C remain tight between the floor and the roof. When the props of the frame `B have been tightened, the two outer frames A and C are advanced by pressurising the two ram cylinders 6 and 7.

If the two cylinders -6 and 7 are double-acting and a xed connection to the conveyor 2 is not desired, the assembly can also advance in the absence of the ram cylinder 9 and the tie rope 8.

The props 2 of the centre frame B are connected to the props 2 of the frame A by steering cylinders 11 and 12. The steering cylinders are linked to lugs 13 which are themselves afixed to the upper ends of the cylinders of the props 2. The piston rod ends of the -cylinders 11 and 12 are likewise linked to lugs 13 which are axed to the cylinders 20 of the props 2 of the centre frame.

The props 2 of the other outer frame C are connected to the props 2 of the centre frame B by steering cylinders 14 and 15. The disposition of the cylinders 14 and 15 and of their piston rods corresponds to that of the two cylinders 11 and 12. It will also be understood from the drawing that the steering cylinders 11, 14 and 12, 15 are associated in pairs inasmuch as each of the two steering cylinders of a pair is connected to one of the outer frames A or C and both are linked at the same level to the centre frame. The points of attachment to the centre frame are therefore in common vertical and horizontal planes of the centre frame. Moreover, since the pairs comprising the cylinders 11, 14 and 12, 15 are also otherwise of identical construction, only one of these units need be hereinafter described in greater detail.

As indicated in the drawing, the cylinders 11 and 14 differ with respect to their diameters. The object of this difference in diameters in the illustrated embodiment is to ensure that the effective annular cross-section in cylinder 11 is exactly the same as the full cross-section of the piston in cylinder 14. It follows that the, swept volumes in the cylinder chamber containing the piston rod in cylinder 11 and the swept volume in the cylinder chamber on the side facing away from the piston cylinder 14 are equal for identical piston strokes.

The hydraulic control system illustrated in FIGURE 3 comprises a multi-position piston valve having control positions 31, 32 and 33. In position 32, as shown, the annular chamber on the piston rod side in cylinder 11 is connected through pipes 34, 35 and 36 to the chamber facing away from the piston rod end in cylinder 14.

If the ram cylinder 9 is pressurised in this position of the valve, the frame B will move from the position it is shown to occupy in FIGURE 2 into that shown in FIG- URE 3. ".[he centre frame B will be steered in absolute parallelism to the two outer frames A and C. Naturally this will also apply when the centre frame B is tight and the outer frames A and C are advanced.

However, assuming that the two outer frames A and C are tight and the centre frame B tends to follow the point of attachment of the rope 8 to the conveyor when the latter tends to migrate, then the two props 2 in frame B will pe pulled ino a position of Obliquity. They are not thereby constrained because the two cylinders 11 and 12 can still freely interchange the volumes of iluid they contain,

However, the chamber on the side opposite the piston rod end in cylinder 11 and the chamber containing the piston rod in cylinder 14 are interconnected through the pipes 37, 38 and 39. If the multi-position valve 30 in FIGURE 3 is displaced to the right in FIGURE 3, the pump 21 will force fluid into the pipe 38 and hence through the pipe 37 into the chamber in the cylinder 11 facing away from the piston rod end and through the pipe 39 into the chamber containing the piston rod in the cylinder 14. Consequently the piston rod of the cylinder 11 will be forced outwards and the piston rod in'the` cylinder 14 will be pulled inwards. In position 31 of the piston valve 30 it is the other chambers in the two cylinders that will be thus pressurised.

The safety valve 40 serves to protect the pipe lines 35 and 36.

It will thus be understood that under normal conditions, i.e. when the point of attachment of the rope 8 to the conveyor does not migrate, the steering cylinder units permit the frames A, C and B to advance in parallel the one to the other and that step-wise advance can proceed without steering or corrective action. However, when the point of attachment of the rope 8 to the conveyor moves out of the direction of advance, then the differential action of the cylinder pairs in the assembly, as described, will cause the props to be realigned.

The required hydraulic control system is particularly simple because the steering cylinders take automatic corrective action when the ram cylinders operate.

What is claimed is:

1. A control system for the parallel steering of a roof support system comprising three frames arranged side by side, each frame having roof and base bars and a pair of interposed telescoping props, members connecting the outermost frames enabling them to move together independently of the central frame, a hydraulic ram piston and cylinder assembly interposed between each of the outermost frames and the central frame, means for pivotally attaching the 'cylinders of said assemblies to the outermost frames respectively, means for pivotally attaching the ram pistons of said assemblies to the central frame respectively, an anchorage, a hydraulic ram piston and cylinder assembly connected to the central frame, a flexible connection between said last piston and cylinder assembly and said anchorage, steering means comprising a pair of spaced piston and cylinder assemblies connecting each of said outer frames and said central frame, means for conducting pressure uid to one end or the other of said last piston and cylinder assemblies, respectively, for correcting an unparallel condition of the central frame with respect to the outer frames, and control means for said last pressure fluid means.

2. A control system as claimed in claim 1, comprising means for connecting the pistons and cylinders of said steering means to appropriate prop cylinders.

References Cited UNITED STATES PATENTS 3,216,201 1l/1965 Kibble et al 61-45 3,324,664 6/1967 AllenA 6l-45 3,362,169 1/ 1968 Groetschel 61-45 FOREIGN PATENTS 830,342 3/ 1960 Great Britain.

874,435 8/ 1961 Great Britain.

972,506 lO/ 1964 Great Britain.

999,943 7/ 1965 Great Britain. 1,078,514 3/ 1960 Germany.

DENNIS L. TAYLOR, Primary Examiner 

